ADT Fire and Security and the Amalgamated Engineering and Electrical Union (AEEU) have yet to reach agreement over plans to fit tracking devices to its fleet of 1,500 vans. The union had threatened legal action under the Human Rights Act if the company went ahead with plans to fit the black boxes to its fleet.

The AEEU claimed the company would be able to spy on staff at weekends. A spokesman for the union said discussions between the two parties were still in progress.